Atomic resonance line source lamps and spectrophotometers for use with such lamps

ABSTRACT

An improved source lamp assembly for use in atomic absorption spectrophotometers is described having encoded structures for identifying the atomic element of the source lamp assembly, as well as to represent lamp operating current. The encoding structures are formed by way of mechanical, optical, or magnetic means. In particular, a mechanical arrangement involves a plurality of projections and recesses, either formed relative to a base structure of the lamp assembly or relative to an attached card-like structure. A card reading device is used to read this card-like structure. These alternative arrangements can be also used relative to optical encoding or magnetic encoding.

This application is a continuation-in-part application of Ser. No.436,205, filed Oct. 25, 1982, now abandoned for continuation applicationSer. No. 744,648, filed June 13, 1985, and all common subject matter andall benefits of these applications are hereby claimed.

This invention relates to atomic resonance line source lamps andspectrophotometers for use with such lamps.

Atomic absorption spectrophotometer source lamp assemblies are knownhaving a lamp for producing resonance line radiation characteristic ofone or more atomic elements when operated by lamp power supply means.Atomic absorption spectrophotometers are also known including amonochromator for passing radiation of a selected wavelengthcharacteristic of an atomic element when that radiation is emitted by asource lamp for producing resonance line radiation, and wavelengthcontrol means responsive to wavelength information applied thereto forsetting the monochromator to the selected wavelength.

Such known lamp assemblies are labelled to identify the one or moreatomic elements to the person using the spectrophotometer who then hasthe task of entering into such known spectrophotometers the wavelengthinformation for setting the monochromator. Disadvantages of this taskare that it involves the possibility of error on the part of the userand also limits the extent of possible automatic operation of thespectrophotometer.

An object of the invention is to overcome these disadvantages.

The invention provides a source lamp assembly as described in the secondparagraph of this specification, characterised in that the lamp assemblyincludes an electrical network representative of one or more atomicelements and connecting means for connecting the network to measurementcircuit means in an atomic absorption spectrophotometer enablingidentification of the one or more atomic elements in thespectrophotometer.

The invention further provides an atomic absorption spectrophotometer asdescribed in the second paragraph of this specification, characterisedin that the spectrophotometer is adapted for use with a source lampassembly as described in the previous paragraph with thespectrophotometer including measurement circuit means, a microprocessorand a memory holding wavelength information at a location thereinassociated with each of the respective one or more atomic elements of aplurality of lamps with, the microprocessor being conditioned toidentify the one or more atomic elements of a lamp assembly whosenetwork is connected to the measurement circuit means responsive tomeasurement of the respective network by the measurement circuit means,and the microprocessor being conditioned to apply to the wavelengthcontrol means wavelength information derived from the memory for anatomic element which is so identified.

Known lamp assemblies as described in the second paragraph of thisspecification and in which the lamps are single atomic element ormultiple atomic element hollow cathode lamps are labelled to identify amaximum lamp operating current to the person using the spectrophotometerwho then has the task of choosing and putting into effect a suitablelamp operating current. This again involves the possibility of error andlimits the extent of possible automatic operation.

In a lamp assembly which is according to the invention and furthermorein which the lamp is a single atomic element or multiple atomic elementhollow cathode lamp, the network may be further representative of a lampoperating current. An advantage here is that during the useful lifetimeof a spectrophotometer the characteristics of a hollow cathode lamp fora particular atomic element or combination of atomic elements, inparticular the maximum lamp operating current, may change. Aspectrophotometer according to the invention may be adapted for use withsuch a source assembly with the spectrophotometer including the lamppower supply means and the read only memory holding lamp currentinformation and with the microprocessor being conditioned to control thelamp power supply means using, together with the lamp currentinformation from the read-only memory, further lamp current informationderived by the measurement circuit means from a lamp assembly networkconnected thereto.

In a spectrophotometer according to the invention, an analysisconsisting of the operation of the spectrophotometer to analyse one ormore samples in respect of an atomic element of a lamp assembly may becontrolled by the microprocessor being conditioned to use an informationset continuously stored in a read-write memory for at least the durationof that analysis, in which case the information set has atomic elementrelated information, including wavelength information, derivable fromthe read-only memory for that atomic element, together with samplerelated information derivable from elsewhere for one or more samples.Both atomic element related information and sample related informationare needed for an analysis, and bringing them both into such aninformation set in the manner described for use by the microprocessorhas the advantage of further facilitating automatic operation of thespectrophotometer in an analysis using a lamp assembly according to theinvention.

A spectrophotometer as described in the previous paragraph may haveholding and positioning means for holding more than one lamp assembly ata time with the networks of all the lamp assemblies so held beingconnected to the measurement circuit means and for positioning one lampat a time of the lamp assemblies so held in the optical path of themonochromator, in which case an analysis sequence consisting of theoperation of the spectrophotometer to analyse the one or more samples inrespect of each of a set of atomic elements in turn, wherein the sourcelamp for each atomic element of the set is part of a lamp assembly, iscontrolled by the microprocessor being conditioned to control theholding and positioning means to position a lamp emitting radiationcharacteristic of each atomic element of the set of elements in turn inthe optical path of the monochromator and by the microprocessor beingconditioned to use each of a plurality of information sets in turn, oneinformation set for each atomic element of the set of elements with theplurality of information sets being continuously stored in theread-write memory for at least the duration of the analysis sequence.This arrangement has the advantage of facilitating automatic operationof the spectrophotometer in such an analysis sequence in respect of aset of atomic elements.

Embodiments of the invention will now be described in more detail withreference to the accompanying drawings in which:

FIG. 1 shows a schematic section view of a single atomic element hollowcathode lamp assembly according to the invention and electricalconnectors directly associated therewith,

FIG. 2 shows a perspective view of the lamp assembly of FIG. 1,

FIG. 3 shows the resistor network of the lamp assembly of FIG. 1 andmeasurement circuit means of a spectrophotometer using that lamp,

FIG. 4 shows an atomic absorption spectrophotometer according to theinvention using four lamp assemblies as in FIG. 1,

FIG. 5 is a flow chart of an operation of the spectrophotometer shown inFIG. 4,

FIG. 6 shows schematically a side elevation and an end elevation of asecond embodiment of a resonance line source lamp in the form of ahollow cathode lamp assembly for use in a spectrophotometer according tothe invention,

FIG. 7 is a perspective view of a third embodiment of a resonance linesource lamp in the form of a hollow cathode lamp assembly for use in aspectrophotometer according to the invention,

FIG. 8 shows the hollow cathode lamp assembly of FIG. 7 together with acard reader,

FIG. 9 shows a cross-sectional view on line A--A of the card readershown in FIG. 8,

FIG. 10 shows the hollow cathode lamp assembly of FIG. 6 in combinationwith mechanical sensors,

FIG. 11 shows schematically a side elevation and an end elevation of afourth embodiment of a resonance line source lamp in the form of ahollow cathode lamp assembly for use in a spectrophotometer according tothe invention,

FIG. 12 shows the hollow cathode lamp assembly of FIG. 6 in combinationwith a sensor,

FIG. 13 shows a lamp turret carrying four of the lamps shown in FIG. 7and four card readers,

FIG. 14 shows schematically a fifth embodiment of a resonance linesource lamp in the form of a single element hollow cathode lamp bearinga magnetic code on its outer surface,

FIG. 15 is a perspective view of a hollow cathode lamp having a cardbearing a magnetic code attached thereto,

FIG. 16 shows a lamp turret carrying four of the lamps shown in FIG. 2and four magnetic code readers,

FIG. 17 shows schematically a sixth embodiment of a resonance linesource lamp in the form of a single element hollow cathode lamp bearingan optical code on its outer surface,

FIG. 18 is a perspective view of a hollow cathode lamp having a cardbearing an optical code attached thereto, and

FIG. 19 shows a lamp turret carrying four of the lamps shown in FIG. 18and four optical code readers.

Referring now to FIGS. 1 and 2, a single atomic element hollow cathodelamp assembly HCL has a lamp formed by a hollow cathode electrode CA andan anode electrode AN within a sealed envelope SE. A base BA is attachedto the envelope SE, and located within the base BA is a resistor networkRN consisting of four resistors R1, R2, R3 and R4 connected to a commonlead EL. Two plug terminals P6 and P7 protruding from the base BA andconnected respectively to the electrodes CA and AN provide connectingmeans for connecting these electrodes to lamp power supply means LPS(see FIG. 4). Five plug terminals P1 to P5 protruding from the base BAand connected respectively to the resistors R1 to R4 and the lead ELprovide further connecting means for including the resistor network inmeasurement circuit means MCM (see FIGS. 3 and 4) in an atomicabsorption spectrophotometer. The resistor network is representative ofthe atomic element of the lamp by virtue of the resistors R1 and R2 andis furthermore representative of a lamp operating current by virtue ofthe resistors R3 and R4. As shown in FIG. 2, the terminals P1 to P7 arearranged in a conventional octal plug configuration with a boss BA1 onthe base BA for ensuring correct electrical connection.

When in the operative position in a spectrophotometer, the lamp assemblyHCL will be located in the optical path thereof and electricalconnection from the terminals P1 to P7 to a fixed socket SK in thespectrophotometer will be made via a connecting lead CL with socket andplug connectors. Instead of being located within the base BA theresistor network RN could possibly be located within the connecting leadCL, and in this case the lead CL can be considered as forming part ofthe lamp assembly with appropriate parts of the lead CL providing partof the connecting means for the electrodes and providing the whole ofthe further connecting means for the network. Another possibility wouldbe to locate the network RN inside the sealed envelope SE. Both thesepossible variations from the arrangement shown in FIGS. 1 and 2 indicatethat it is not necessary for the lamp to be provided with a separatelyidentifiable base.

Referring now to FIG. 3, the resistor network RN is shown together withmeasurement circuit means MCM and a microprocessor μP in aspectrophotometer. The measurement circuit means MCM includes amultiplexer MPX and an analogue-to-digital converter ADC respectivelycontrolled by and connected to the microprocessor μP via a bus BS, and aresistor R5 connected to a voltage source +V. By means of themultiplexer MPX the resistors R1 to R4 are connected in turn in serieswith the resistor R5 and the common lead EL and hence the voltage acrosseach of the resistors R1 to R4 in turn is applied to theanalogue-to-digital converter ADC. The ohmic values of the two resistorsR1 and R2 together represent the atomic element of the single atomicelement hollow cathode lamp assembly incorporating the network;conveniently one of these two resistors represents the tens value andthe other resistor represents the units value of the atomic number ofthe atomic element. The ohmic values of the two resistors R3 and R4together represent a lamp operating current; conveniently the maximumoperating current for the electrodes of the lamp assembly incorporatingthe network. The microprocessor μP is conditioned to identify the atomicelement responsive to measurement of the resistor network by themeasurement circuit means MCM, that is to say the two successive digitaloutputs of the converter ADC responsive to the resistors R1 and R2. Thelamp current information derived by the measurement circuit means MCMfrom the resistor network, that is to say the two successive digitaloutputs of the converter ADC responsive to the resistors R3 and R4, isused by the microprocessor μP together with other lamp currentinformation, as will be described in detail with reference to FIGS. 4and 5, to control the lamp power supply means LPS connected to theelectrodes of the respective hollow cathode lamp.

It will be appreciated that although the resistive network as describedis inexpensive and convenient the electrical network incorporated in thehollow cathode lamp assembly as described above to represent the atomicelement and the maximum lamp operating current could be other thanresistive. With suitably adapted measurement circuit means, the networkcould for example be capacitive or it could provide a binaryrepresentation by using connections which are open or short circuit orby using diodes.

The single atomic element hollow cathode lamp provided with anelectrical network as described above with reference to FIGS. 1 and 2 isone example of a lamp assembly according to the invention. Other lampsfor producing resonance line radiation characteristic of one or moreatomic elements when operated by lamp power supply means may be providedwith similar networks to form atomic absorption spectrophotometer sourcelamp assemblies according to the invention. One such other lamp is anelectrodeless discharge lamp. In this case an electrical network may besimilarly provided in an assembly with the lamp to enable the singleatomic element for which the lamp emits resonance line radiation to beidentified in the spectrophotometer. Electrodeless discharge lamps areusually provided with an auxiliary power supply external to thespectrophotometer. The network in the lamp assembly in this case couldalso represent a particular value of electrical power which isidentified in the spectrophotometer and used to control the auxiliarypower supply. Another such other lamp is a multiple atomic elementhollow cathode lamp. In this case also an electrical network may beprovided in an assembly with the lamp to enable all the atomic elementsfor which the lamp emits resonance line radiation to be identified inthe spectrophotometer. Multiple atomic element hollow cathode lampsconventionally emit resonance line radiation for particular combinationof two, three or four atomic elements, and the network could representthese atomic elements individually or it could represent the particularcombination. The network could also represent a maximum lamp current ina manner similar to that described above for a single atomic elementhollow cathode lamp.

Referring now to FIG. 4, there is shown an atomic absorptionspectrophotometer holding four single atomic element hollow cathode lampassemblies HCL1 to HCL4 each in accordance with the lamp assembly HCLdescribed above with reference to FIGS. 1 and 2 and each connected tomeasurement circuit means MCM and a microprocessor μP essentially asdescribed above with reference to FIG. 3. The four lamp assemblies HCL1to HCL4 are held in a turret TU operated by turret control means TUC toposition a selected one of the four lamp assemblies HCL1 to HCL4 at atime in the optical path of the spectrophotometer. FIG. 4 shows the lampassembly HCL1 in the optical path. Radiation emitted by the lampassembly HCL1 passes from the respective cathode CA1 through an atomiserAT which may be of the conventional flame type or electrothermal furnacetype. Samples to be analysed by the spectrophotometer are fed into theatomiser AT from an automatic sampler AS operated by automatic samplercontrol means ASC and the atomiser is operated by atomiser control meansATC. Having passed through the atomiser AT, the radiation passes througha monochromator MN. The wavelength of the radiation passed by themonochromator MN is selected by wavelength control means MWC and thebandpass, that is to say the slit width, of the monochromator MN isselected by slit control means MSC. A photomultiplier tube detector DETprovides an electrical voltage signal whose amplitude is proportional tothe intensity of radiation emerging from the monochromator MN, and alogarithmic converter LG provides an amplified voltage signalproportional to the logarithm of the output of the detector DET. Theconcentration of the atomic element in respect of which the samplespresented to the atomiser AT are analysed is essentially proportional tothe output signal of the logarithmic converter LG.

The two electrodes of each of the lamp assemblies HCL1 to HCL4 areconnected to the lamp power supply means LPS with only the hollowcathode electrodes CA1 etc being schematically shown in the Figure witha single connection in each case. The resistor networks RN1 to RN4 ofthe respective lamp assemblies HCL1 to HCL4 with each network havingfour respective resistors R1 to R4 as shown in FIGS. 1 and 3, areconnected to a multiplexer MPX1. For simplicity of illustration only oneconnection is shown from each of the networks RN1 to RN4 to themultiplexer MPX1 although there is an individual connection from each ofthe sixteen resistors therein to the multiplexer MPX1. Each of thesesixteen network resistors is connected in turn in series with theresistor R5 to the voltage source +V via the multiplexer MPX1 controlledby latch circuit means LH. The voltage across each of the sixteennetwork resistors is connected in turn to the analogue-to-digitalconverter ADC via a further multiplexer MPX2 which is also controlled bythe latch circuit means LH. The multiplexers MPX1 and MPX2, the resistorR5, the voltage source +V, the latch circuit means LH and theanalogue-to-digital converter ADC form the measurement circuit means MCMto which the networks RN1 and RN4 are connected. The output signal ofthe logarithmic converter LG is also connected to theanalogue-to-digital converter ADC via the multiplexer MPX2. In operationof the spectrophotometer the networks RN1 to RN4 are measured by themeasurement circuit means MCM as soon as the lamp assemblies HCL1 toHCL4 are connected thereto. Thereafter this measurement is repeated as abackground check routine which is interrupted when it is necessary foranother analogue signal produced by the spectrophotometer, for examplethe output of the logarithmic converter LG, to be applied to theanalogue-to-digital converter ADC via the multiplexer MPX2. Thebackground check routine can be used, for example, to provide an errorsignal if a lamp is not present in a required position.

A microcomputer MCP includes the microprocessor μP, a volatileread-write memory RAM for temporarily holding data for processing by themicroprocessor μP, and a read-only memory ROM holding programinformation for conditioning the operation of the microprocessor μP. Itshould be noted that the read-only memory ROM is a convenient andinexpensive device for storing unchanging information and has thefurther advantage of being resistant to data corruption caused byelectrical interference or power supply interruptions. However, thefunction performed by the read-only memory ROM could be performed byother types of memory, for example various types of read-write memorysuch as magnetic tape or disc or semiconductor RAM with back-up batterysupply. The bus BS connects the microprocessor μP to the read-writememory RAM, to the read-only memory ROM, to the analogue-to-digitalconverter ADC, to the latch circuit means LH, to the lamp power supplyLPS, to the turret control means TUC, to the automatic sampler controlmeans ASC, to the atomiser control means ATC, to the slit control meansMSC and to the wavelength control means MWC.

In addition to holding program information the read-only memory ROM alsoholds atomic element related information, including in particularwavelength information, at a location therein associated with therespective atomic element of each of a plurality of single atomicelement hollow cathode lamp assemblies with which the spectrophotometermay be used. There may be in excess of sixty such single atomic elementhollow cathode lamp assemblies but at any one time only one or some ofthese lamp assemblies, for example the four lamp assemblies HCL1 toHCL4, will be located in the spectrophotometer with their networksconnected to the measurement circuit means MCM. The microprocessor μP isconditioned to identify the atomic element of the one or some lampasemblies whose networks are connected to the measurement circuit meansMCM responsive to measurement of the respective network thereby. In thecase of the four lamp assemblies HCL1 to HCL4 shown in FIG. 4 thisidentification is responsive to the output of the analogue-to-digitalconverter ADC in respect of the voltages measured successively acrossthe resistors R1 and R2 of the respective networks RN1 to RN4 of thelamp assemblies. The microprocessor μP is further conditioned to applyto the wavelength control means MWC wavelength information derived fromthe read-only memory ROM for that one of the one of some of the lampassemblies whose atomic elements are identified and the lamp of whichfurthermore is present in the optical path of the monochromator. Theturret TU and turret control means TUC include means which enable themicroprocessor μP to identify the lamp present in the optical path ofthe monochromator.

The read-only memory ROM also holds lamp current information. Themicroprocessor μP is conditioned to control the lamp power supply meansLPS using this lamp current information for the one or some lampassemblies whose atomic elements are identified via the measurementcircuit means MCM. It is advantageous for the microprocessor μP to usethe maximum lamp current information derived from the networks RN1 toRN4 via the measurement circuit means MCM together with the lamp currentinformation derived from the read-only memory ROM to control the lamppower supply means LPS. Of the networks RN1 to RN4 did not contain theresistors R3 and R4 representative of the maximum lamp operating currentof the respective lamp assemblies, then the lamp current information inthe read-only memory ROM could be held at locations therein associatedwith the respective atomic element of each of the plurality of hollowcathode lamp assemblies with which the spectrophotometer may be used andcould entirely define the operating current for the respective lamps.

For an analysis consisting of the operation of the spectrophotometer toanalyse one or more samples in respect of the single atomic element ofone of the plurality of hollow cathode lamp assemblies for whichinformation is stored in the read-only memory ROM, both atomic elementrelated information and sample related information are needed. Automaticoperation of the spectrophotometer is facilated by both types ofinformation being brought together to form an information set which iscontinuously stored for at least the duration of that analysis in anon-volatile read-write memory NVM. The microprocessor μP is connectedby the bus BS to the memory NVM and is conditioned to use thatinformation set to control that analysis.

The atomic element related information for each information set in thememory NVM is derivable from the read-only memory ROM and transferredthereto by the microprocessor μP upon identification of the atomicelement of the respective lamp assembly. This atomic element relatedinformation will include the wavelength information already mentionedtogether with slit width information for application to the slit controlmeans MSC. In the case where the atomiser AT is of the flame type, theatomic element related information derivable from the read-only memoryROM will include information identifying fuel type and fuel rate forapplication to the atomiser control means ATC and may also includemeasurement time information. The time for which the output signal ofthe detector DET, received via the logarithmic converter LG, multiplexerMPX2 and analogue-to-digital converter ADC, is averaged by themicroprocessor μP for noise reduction of that signal is determined bythe measurement time. In the case where the atomiser AT is of theelectrothermal furnace type, the atomic element related information willagain include wavelength information and slit width information, it willfurthermore include furnace heating cycle information for application tothe atomiser control means ATC, and it may include measurement timeinformation relevant to determining peak height and peak area resultsfrom the output signal of the detector DET.

The sample related information for each information set in the memoryNVM may be entered into an appropriate location therein by the user ofthe spectrophotometer via a keypad KPD connected by the bus BS to themicroprocessor μP. This sample related information will include thenumber of standard concentration samples to be held in the automaticsampler AS and information identifying the concentration of thosestandard samples. The feature of background correction, which is wellknown and therefore not otherwise mentioned in this specification, willnormally be provided for use in the spectrophotometer and the samplerelated information will in this case also indicate whether or notbackground correction is to be used in a particular analysis. The atomicelement related information may also include an overriding instructionto switch off background correction for atomic elements for which thewavelength of radiation to be passed by the monochromator is above acertain value.

The results of an analysis of one or more samples in respect of a singleatomic element are temporarily stored in the volatile read-write memoryRAM of the microcomputer MCP and eventually outputted to a suitablerecorder, for example a printer PRI shown connected by the bus BS to themicroprocessor μP, and possibly also to a display (not shown).

It is convenient to mention here that the automatic sampler AS will beof a type specifically appropriate for use either with a flame typeatomiser AT or an electrothermal furnace type atomiser AT as the casemay be. Furthermore the automatic sampler control means ASC willnormally partly be specific to and located in the particular automaticsampler AS and partly be permanently associated with the microprocessorμP and located in the main body of the spectrophotometer. It is wellknown for atomic absorption spectrophotometers to be primarily providedwith one type of atomiser and to be adaptable for use with the othertype of atomiser as an accessory. For example it is known to have anatomic absorption spectrophotometer which is primarily for use in theflame mode but adaptable for use in the electrothermal mode; and in thiscase the atomiser control means ATC for the electrothermal furnace willnormally be provided as an accessory with that furnace rather than beinglocated in the main body of the instrument and permanently associatedwith the microprocessor μP. Appropriate sensors (not shown) will beprovided so that the type of atomiser AT and automatic sampler AS areidentified to the microprocessor μP for appropriate operation. In thecase mentioned where the atomiser control means ATC is provided as anaccessory part of the spectrophotometer it can have its own non-volatileread-write memory to hold a plurality of sets of furnace heat cycleinformation, and this information which has been mentioned above asbeing derivable from the read-only memory ROM may instead remain in thenon-volatile read-write memory of the electrothermal furnace atomisercontrol means ATC which may then be considered as part of thenon-volatile read-write memory NVM holding the total information set foran analysis.

The non-volatile read-write memory NVM has the capacity to store aplurality of information sets as described above. Thus an analysissequence consisting of the operation of the spectrophotometer to analyseone or more samples held in the automatic sampler AS in respect of eachof a set of atomic elements in turn is controlled by the microprocessorμP being conditioned to use each of the plurality of information sets inturn, one information set for each atomic element of the set ofelements. The plurality of information sets will be continously storedin the read-write memory NVM for at least the duration of the analysissequence. For example, the memory NVM will have the capacity to store atleast four information sets, one for each of the four single atomicelement hollow cathode lamp assemblies HCL1 to HCL4 shown in FIG. 4.With the use of four such lamp assemblies, the atomic element relatedinformation in each information set is derivable from the read-onlymemory ROM. The spectrophotometer may additionally be able to use lampsother than the lamp assemblies according to the invention which havenetworks identifying the respective atomic element. For example in eachof the four turret lamp locations there may be accommodated aconventional single atomic element hollow cathode lamp. In this case theuser of the spectrophotometer may simply provide, via the key pad KPD,information to the microprocessor μP identifying the atomic element ofeach lamp and in response thereto the microprocessor μP can derive allthe necessary atomic element related information from the read-onlymemory ROM and transfer it for use into the non-volatile memory NVM. Ina more precise reproduction of the function of any one of the resistornetworks RN1 to RN4, the user could also provide information via the keypad KPD corresponding to the lamp current information of those networks.As another example, conventional electrodeless discharge lamps may beaccommodated in each of the four turret lamp locations. In this caseagain the user will provide via the key pad KPD information identifyingthe respective atomic element of the lamp, and additionally the userwill have to provide information for an auxiliary power supply foroperating electrodeless discharge lamps. As another example, multipleatomic element hollow cathode lamps may be used. These lamps may beconventional, in which case the user will provide via the keypad KPDinformation identifying the lamp as a multiple element lamp, informationidentifying the atomic elements of the lamp and lamp currentinformation. A possible modification is that the multiple atomic elementhollow cathode lamp may be provided with a resistor network, to bemeasured by the measurement circuit means MCM, by which it will providelamp current information and information identifying it as amultielement lamp. The user will then provide information via the keypadKPD identifying the atomic elements of the lamp and the microprocessorμP will be conditioned to derive atomic element related information fromthe read-only memory ROM and transfer it to a separate information setin the non-volatile read-write memory NVM for each of those atomicelements.

In addition to the ability to use lamps other than the lamp assembliesaccording to the invention, the spectrophotometer may be provided with amanual override facility such that even when a lamp assembly having anetwork according to the invention is present the user will be able toenter, via the keypad KPD, atomic element related information into aninformation set in the non-volatile read-write memory NVM which isdifferent to the information which would otherwise be derived from theread-only memory ROM.

An external computer (not shown) may be connected via a suitableinterface circuit to the bus BS. One use of an external computer can beto further facilitate automatic operation of the spectrophotometer byaugmenting the function of the non-volatile read-write memory NVM. Forexample once an information set consisting of atomic element relatedinformation and sample related information as described above has beenentered into the non-volatile memory NVM for a particular analysis, thatinformation set may be transferred to the external computer for recallat any later date for use in repetition of the same analysis even thoughthe capacity of the non-volatile memory NVM may have been fully used fordifferent analyses in the meantime.

It will be appreciated that in the above description of an atomicabsorption spectrophotometer with respect to FIG. 4, only those featuresof such a spectrophotometer have been mentioned which are relevant tothe invention and there are other features which conventionally arepresent or may be present. For example, the lamp power supply isnormally modulated and the signal from the detector DET iscorrespondingly demodulated prior to processing by the logarithmicconverter LG. Also the detector DET will be subject to gain controlwhich may be automatic. Also double beam operation, that is theprovision of a reference optical path which bypasses the atomiser andthe use of the signal derived via this reference path to providebaseline correction which counteracts instrumental drift, particularlyof the hollow cathode lamp output and the detector output, is a wellknown optional feature of atomic absorption spectrophotometers. In thecase of the spectrophotometer described above with reference to FIG. 4which is capable of automatic operation for a long period of time,double beam operation will be particularly advantageous and very likelyincorporated.

Referring now to FIG. 5, there is shown a flow chart of an operation ofthe spectrophotometer shown in FIG. 4.

In operation 1 "Switch On" the user switches on the electrical suppliesto the spectrophotometer. In operation 2 "Initialise", the user ensuresthat the four single atomic element hollow cathode lamp assemblies HCL1to HCL4 are loaded by being located in the turret TU and electricallyconnected, and that four corresponding information sets are located inthe non-volatile read-write memory NVM. There will be only one loadingposition for the lamps which will coincide with the position in which alamp is located on the optical axis of the spectrophotometer, that is tosay the position of the lamp assembly HCL1 as shown in FIG. 4. As eachlamp assembly is loaded in turn the microprocessor μP can transfer therelevant atomic element related information for the respectiveinformation set from the read-only memory ROM into an appropriatelocation in the non-volatile memory NVM responsive to measurement of therespective one of the lamp assembly networks RN1 to RN4 by themeasurement circuit means MCM. At the time that each lamp is in theloading position the user can enter the relevant sample relatedinformation for the respective information set into the memory NVM viathe key pad KPD and the microprocessor μP. It may be that the operationof the spectrophotometer is to be a repeat, for a new set of samples inthe automatic sampler AS, of an immediately preceding analysis sequencefor a different set of samples in respect of the atomic elements of thesame lamp assemblies HCL1 to HCL4. If this is the case, the lampassemblies will already be loaded and the corresponding information setswill be present in the non-volatile memory NVM prior to "Switch On" andthe "Initialise" operation 2 will not need to be performed by the user.In operation 3 "Power to Lamps" the user switches on the lamp powersupply means LPS to each lamp in turn and responsive to this action foreach lamp in turn the appropriate lamp current information is derivedfrom the non-volatile memory NVM by the microprocessor μP and applied tothe lamp current supply means LPS. In the case where the atomiser AT isof the flame type an operation (not shown) after either operation 2 or 3and involving action by the user is required to ignite the flame of theatomiser AT. In operation 4 "Start Automatic Sampler" the userinitialises the operation of the automatic sampler AS, and responsive tothis operation appropriate information is entered from the automaticsampler control means ASC into the read-write memory RAM after which theoperation of the spectrophotometer can be entirely automatic undercontrol of the microprocessor μP without further intervention by theuser.

Responsive to operation 4, the microprocessor μP performs operation 5"Set N=1". N represents a turret count. The turret count N determineswhich one of the four lamp assemblies HCL1 to HCL4 should be in theoptical path for the duration of a run of the automatic sampler AS, thatis to say an analysis of the samples therein for one atomic element, andit also determines which information set in the non-volatile memory NVMwill be used by the microprocessor μP during that analysis. The turretcount N is held in the read-write memory RAM for the duration of eachanalysis. Responsive to operation 5, the microprocessor μP performsoperation 6 "Set Lamp Turret to N". In this operation the turret TU isdriven to position N (At this stage N=1 corresponding to say the lampassembly HCL1) by the turret control means TUC. Responsive to operation6, the microprocessor μP controls operation 7 "Set Slits" in which themonochromator MN slit width is set by the slit control means MSC usingslit width information from the information set in the non-volatilememory NVM, and then the microprocessor μP controls operation 8 "SetWavelength" in which the monochromator MN wavelength is set by thewavelength control means MWC using wavelength information from theinformation set in the non-volatile memory NVM. As is conventional, thegain of the detector DET will be automatically adjusted in conjunctionwith setting the monochromator wavelength. Also responsive to operation6 the microprocessor μP will transfer measurement time information fromthe non-volatile memory NVM to the volatile read-write memory RAM foruse by the microprocessor μP during subsequent measurements of thesamples for the one atomic element.

Following operation 8, the microprocessor μP controls operation 9"Measure Blank". In this operation, under control of the automaticsampler control means ASC, the automatic sampler AS provides a sample tothe atomiser AT having nominally zero concentration of the one atomicelement for which the set of samples are to be analysed. This sample isatomised by the atomiser AT under control of the atomiser control meansATC, and the output signal of the detector DET is passed via thelogarithmic converter LG and the multiplexer MPX2 andanalogue-to-digital converter ADC of the measurement circuit means MCMto the microprocessor μP and the result is stored in the read-writememory RAM as a baseline measurement representing zero concentration ofthe atomic element for the duration of the analysis of the set ofsamples for that atomic element. In the case where the atomiser AT is ofthe flame type, the microprocessor μP will apply fuel type and fuel rateinformation from the non-volatile memory NVM to the atomiser controlmeans ATC for the atomisation of this and all subsequent samples in theanalysis for the particular atomic element. In the case where theatomiser AT is of the electrothermal furnace type, the microprocessor μPwill apply furnace heating cycle information from the non-volatilememory NVM to the atomiser control means ATC for the atomisation of thisand all subsequent samples in the analysis for the particular atomicelement. Following operation 9, the microprocessor μP controls operation10 "Measure Standards". In this operation, a predetermined number ofstandard, i.e. known concentration samples, which number is present inthe relevant information set in the non-volatile memory NVM, areprovided in turn by the automatic sampler AS to the atomiser AT. In eachcase the detector DET output signal is fed via the measurement circuitmeans MCM to the microprocessor μP and an absorbance result iscalculated by comparison with the baseline measurement in the read-writememory RAM and then stored in the read-write memory RAM. Followingoperation 10, the microprocessor μP performs operation 11 "Calibration".In this operation the microprocessor μP derives the known concentrationvalues of the standard samples from the relevant information set in thenon-volatile memory NVM and uses these concentration values togetherwith the absorbance results for the standard samples, which have beenstored in the read-write memory RAM in operation 10, to calculate a setof calibration coefficients which are then stored in the read-writememory RAM for the duration of the analysis for the one atomic element.These calibration coefficients enable the functions conventionally knownas scale expansion and curvature correction to be applied to subsequentsample measurements.

Following operation 11, the microprocessor μP controls operation 12"Measure Sample, Calculate and Store Concentration". In this operation,a sample from the set of samples which is to be analysed in respect ofthe single atomic element is provided by the automatic sampler AS to theatomiser AT. The absorbance result for that sample derived from theoutput signal of the detector DET is applied to the read-write memoryRAM, the calibration coefficients in the read-write memory RAM areapplied to the absorbance result to produce a concentration result, andthe concentration result is stored in the read-write memory RAM.Following operation 12, the microprocessor μP controls operation 13"Automatic Sampler End?". In this operation the automatic samplercontrol means ASC senses whether or not the automatic sampler AS hasreached the end of its run and does not have a further sample to bemeasured. If the answer is "No", operation 12 is repeated for the nextsample. When operation 12 has been performed for all the samples andtheir respective concentration results stored in the read-write memoryRAM, the next operation 13 will produce the answer "Yes" and themicroprocessor μP will proceed to operation 14 "N=Limit?". In thisoperation the turret count N is checked to determine whether or not itcorresponds to the number of turret positions, for example four turretpositions as shown in FIG. 4. For the first analysis N=1 as set byoperation 5, and so operation 14 produces the answer "No" in response towhich the microprocessor μP performs operation 15 "N=N+1" in which itincrements the value of the turret count N. Responsive to operation 15,the microprocessor μP performs operation 6 in which the turret TU isdriven to the next position to bring the next lamp assembly HCL2 intothe optical path of the spectrophotometer and operations 7 to 13 arerepeated to provide another set of concentration results in theread-write memory RAM for the same set of samples in the autosampler ASin respect of the single atomic element of the next lamp assembly HCL2.When eventually operation 14 produces the answer "Yes" themicroprocessor μP performs operation 16 "Print Formated Results andStop". In this operation the concentration results of all the samples ofthe set of samples in the automatic sampler AS in respect of the atomicelements of all the single atomic element lamp assemblies HCL1 to HCL4in the turret TU are extracted from the read-write memory RAM informated form and printed by the printer PRI and the spectrophotometeris then stopped, that is to say most of the electrical supplies areswitched off and a dormant condition is set. An analysis sequence for anew set of samples will then require the user to start the wholesequence of operations from operation 1.

A spectrophotometer according to the invention may use lamp assemblieswhich are encoded in many different ways besides the representation ofthe element by a resistive network as shown in FIGS. 1 and 2. FIGS. 6 to19 illustrate lamp assemblies which are mechanically, magnetically, andoptically provided with a code which is representative of the one ormore atomic elements. In order to accommodate these alternative lampassemblies the resistor network RN and the measurement circuit means MCMare replaced by the mechanical, magnetic, or optical code and anappropriate code reader. Thus in FIG. 4 the resistor networks RN1 to RN4would be replaced by the appropriate coding means (mechanical, magnetic,optical etc) and the measurement circuit means MCM would be replaced byan appropriate code reader.

FIG. 6 shows a second embodiment of a resonance line source lamp for usein a spectrophotometer according to the invention in the form of asingle element hollow cathode lamp assembly HCL which comprises a hollowcathode electrode CA and an anode electrode AN within a sealed envelopeSE. A base BA is attached to the envelope SE and carries two terminalpins P1 and P2 to which the anode AN and cathode CA are connected andwhich project from the base BA. These terminal pins provide connectingmeans from a lamp power supply means LPS (see FIG. 4) to the anode ANand cathode CA.

The base BA has a plurality of recesses RE formed around its periphery,the presence or absence of recesses at particular locations around theperiphery of the base forming a digital code. The digital code isrepresentative of the atomic element of the lamp and may also representthe current required by the lamp HCL from the lamp power supply meansLPS. Sensors are arranged to read the code on the base BA and produce anelectrical output dependent on the code which output is fed to amicroprocessor μP in the spectrophotometer (see FIG. 4).

FIG. 7 shows an alternative lamp assembly comprising a hollow cathodelamp HCL having a card CC attached thereto by a string ST which passesthrough a hole in a lug LU on the base BA of the lamp HCL. The card CChas a plurality of cut-outs RE along one edge which form a digital codewhich code represents the atomic element of the lamp and may furtherrepresent the lamp operating current. An alternative form of coding ofthe card CC is to form an array of apertures (punched holes), thepresence or absence of an aperture at a particular position on the cardforming a digital code, which digital code is representative of theatomic element of the lamp and may further represent the lamp operatingcurrent. Typically the apertures are circular but they may take otherforms, for example square or rectangular. The card CC may be replaced bya body having a different form, such as a bar or a rod, the body beingprovided with the recesses and/or projections.

FIG. 8 shows the hollow cathode lamp HCL with the card CC attachedthereto by the string ST inserted into a slot CCS in a card reader CCR.A cross sectional view on line A--A of the card reader CCR is shown inFIG. 9. The card reader CCR comprises a housing CCH having a slot CCS inone wall thereof through which the card CC is inserted. Within thehousing CCH an array of light emitting diodes LED is arranged opposite acorresponding array of photodiodes PHD. When the card CC is fullyinserted in the slot CCS it intercepts the path between the two arraysand hence the presence or absence of apertures in the card at particularlocations can be detected by detecting whether or not a particularphotodiode is illuminated. Cables CRC1 and CRC2 feed signals to thelight emitting diode array LED and from the photodiode array PHDrespectively. Instead of having an array of light emitting diodes itwould be equally possible to provide a single diffuse source of lightwhich the card CC interrupts. Alternatively the sensors for the holes inthe card CC may be mechanical fingers or pneumatic sensors.

FIG. 10 shows the hollow cathode lamp HCL of FIG. 6 together with amechanical sensor arrangement for detecting the presence of recesses inthe base. The lamp HCL is assembled against a base plate BP by anyconvenient means and an arrangement comprising a plurality of regularlyspaced spring loaded fingers SLF is also mounted in a fixed positionrelative to the base plate BP so that when the lamp HCL is assembled onthe base plate the fingers engage the lamp base BA and either enter arecess or are depressed against a restoring spring force to operateassociated micro switches MS.

The lamp shown in FIG. 11 is similar to that shown in FIG. 6 the onlydifference being the way in which the code is formed on the base BA. Asshown in FIG. 11 the code is formed by a series of projections PR on thebase BA of the lamp HCL. The presence or absence of a projection atparticular positions around the periphery of the lamp base forming adigital code which is representative of the atomic element of the lampand may also represent the operating current required by the lamp HCLfrom the lamp power supply means LPS. The projections PR on the lampbase BA may be detected by mechanical sensors such as the spring loadedfingers SLF shown in FIG. 10 or, as shown in FIG. 12, may be detected byarranging a plurality of housings PRH, each containing a light emittingdiode and a photodiode, at regular intervals around the base BA so thatthe projections PR, when present, intercept the optical path between thelight emitting and photodiodes.

FIG. 13 shows a turret TU in the form of a turntable which carries foursource lamps HCL1 to HCL4 and four code readers CCR1 to CCR4. The lampsHCL1 to HCL4 are of the type shown in FIG. 7 and the code readers CCR1to CCR4 each have a slot CCS1 to CCS4 into which the encoded cards CC1to CC4 are inserted. This arrangement has the advantage that thepresence of a card can be continuously monitored and that the type oflamp inserted can also therefore be continuously monitored. Even withoutthe continuous monitoring of the optical code it can be readily detectedwhen a lamp is removed from a lamp socket by monitoring the current fromthe lamp supply means LPS since when the lamp is removed the currentsupplied to that socket will fall to zero.

While the lamp assemblies described with reference to FIGS. 6 to 12 havebeen single atomic element hollow cathode lamps, other lamps forproducing resonance line radiation characteristic of one or more atomicelements could equally be used. Such lamps include multi-element hollowcathode lamps and electrodeless discharge lamps.

FIG. 14 shows a resonance line source lamp for use in an atomicabsorption spectrophotometer according to the invention in the form of asingle element hollow cathode lamp assembly HCL which comprises a hollowcathode electrode CA and an anode electrode AN within a sealed envelopeSE. A base BA is attached to the envelope SE and carries two terminalpins P1 and P2 to which the anode AN and cathode CA are connected andwhich project from the base BA. These terminal pins provide connectingmeans from a lamp power supply means LPS (see FIG. 4) to the anode ANand cathode CA.

A label LA bearing a magnetic strip MCS is affixed to the envelope SE ofthe hollow cathode lamp HCL. The magnetic strip MCS is encoded torepresent the atomic element of the lamp and may also represent thecurrent required by the lamp HCL from the lamp power supply means LPS. Amagnetic code reader MCR is arranged to read the code on the label LAand produce an electrical output dependent on the code which output isfed to a microprocessor μP in the spectrophotometer (see FIG. 4).

FIG. 15 shows an alternative lamp assembly comprising a hollow cathodelamp HCL having a card CC attached thereto by a string ST which passesthrough a hole in a lug LU on the base BA of the lamp HCL. The card CCbears a magnetic strip MCS which is encoded to represent the atomicelement of the lamp and may further represent the lamp operatingcurrent. The card CC could be replaced by a body having a differentform, such as a bar or a rod, bearing the magnetic code. The rod or barcould be formed of magnetic material having alternate north and southpoles along its length to form the magnetic code.

The magnetic code may be comparatively densely formed in which casethere must be relative movement between the reading head and themagnetic strip. This may be accomplished either by moving the head overthe strip, either manually or automatically or by moving the strip pasta stationary head, for example by inserting a card into a slot with thehead located adjacent to the slot. With a less dense code it is possibleto read the code with the magnetic strip and reading device bothstationary, for example using Hall effect devices.

FIG. 16 shows a turret TU in the form of a turntable which carries foursource lamps HCL1 to MCL4 and four code readers MCR1 to MCR4. The lampsHCL1 to HCL4 are of the type shown in FIG. 2 and the code readers MCR1to MCR4 each have a slot CCS1 to CCS4 into which the encoded cards CC1to CC4 are inserted. This arrangement has the advantage that thepresence of a card can be continuously monitored and that the type oflamp inserted can also be continuously monitored if the magnetic code isin a suitable form. Even without the continuous monitoring of themagnetic code it can be readily detected when a lamp is removed from alamp socket by monitoring the current from the lamp supply means LPSsince when the lamp is removed the current supplied to that socket willfall to zero.

While the lamp assemblies described with reference to FIGS. 14 and 15have been single atomic element hollow cathode lamps other lamps forproducing resonance line radiation characteristic of one or more atomicelements could equally be used. Such lamps include multi-element hollowcathode lamps and electrodeless discharge lamps.

As shown in FIG. 17 a resonance line source lamp in the form of a singleelement hollow cathode lamp assembly HCL comprises a hollow cathodeelectrode CA and an anode electrode AN within a sealed envelope SE. Abase BA is attached to the envelope SE and carries two terminal pins P1and P2 to which the anode AN and cathode CA are connected and whichproject from the base BA. These terminal pins provide connecting meansfrom a lamp power supply means LPS (see FIG. 4) to the anode AN andcathode CA.

A label LA bearing an optical bar code is affixed to the envelope SE ofthe hollow cathode lamp HCL. The optical bar code is representative ofthe atomic element of the lamp and may also represent the currentrequired by the lamp HCL from the lamp power supply means LPS. Anoptical code reader OCS is arranged to read the code on the label LA andproduce an electrical output dependent on the code which output is fedto a microprocessor μP in the spectrophotometer (see FIG. 4).

FIG. 18 shows an alternative lamp assembly comprising a hollow cathodelamp HCL having a card CC attached thereto by a string ST which passesthrough a hole in a lug LU on the base BA of the lamp HCL. The card CCbears an optical code which represents the atomic element of the lampand may further represent the lamp operating current.

While an optical bar code and bar code reader are convenient and arewidely used, for example for encoding and automatic reading of goods insupermarkets, any form of optical coding and appropriate reader may beused. It would be possible to encode the card CC by means of punchedholes and to pass the card across the optical path of the instrument sothat as the holes in the card passed across the optical path a signal isproduced by the spectrophotometer detector. This signal could then befed to the microprocessor and decoded to determine the lamp fitted. Itwould be necessary in this case to feed the lamp with a current which issafe for all lamps and to then increase the current to the specifiedvalue when the code had been read. Also a punched card with separatelight source and detector could be used. The card CC could be replacedby a body having a different form, such as a bar or rod, bearing theoptical code.

FIG. 19 shows a turret TU in the form of a turntable which carries foursource lamps HCL1 to HCL4 and four code readers OCR1 to OCR4. The lampsHCL1 to HCL4 are of the type shown in FIG. 2 and the code readers OCR1to OCR4 each have a slot CCS1 to CCS4 into which the encoded cards CC1to CC4 are inserted. This arrangement has the advantage that thepresence of a card can be continuously monitored and that the type oflamp inserted can also therefore be continuously monitored. Even withoutthe continuous monitoring of the optical code it can be readily detectedwhen a lamp is removed from a lamp socket by monitoring the current fromthe lamp supply means LPS since when the lamp is removed from currentsupplied to that socket will fall to zero.

While the lamp assemblies described with reference to FIGS. 1 and 2 havebeen single atomic element hollow cathode lamps other lamps forproducing resonance line radiation characteristic of one or more atomicelements could equally be used. Such lamps include multi-element hollowcathode lamps and electrodeless discharge lamps.

We claim:
 1. An atomic absorption spectrophotometer source lamp assemblycomprisinglamp means for producing resonance line radiationcharacteristic of at least one atomic element, encoding means forrepresenting at least said radiation, and connecting circuit means forconnecting said encoding means to a circuit enabling identification ofsaid at least one atomic element.
 2. A lamp assembly according to claim1, wherein said lamp means includes a base structure, and wherein saidencoding means include a plurality of at least one of projections andrecesses to represent said at least one atomic element.
 3. A lampassembly according to claim 2, wherein said encoding means is located ona periphery of said base structure.
 4. A lamp assembly according toclaim 3, wherein sensing means are arranged for detecting saidprojections and recesses.
 5. A lamp assembly according to claim 4,wherein said encoding means includes a plurality of recesses at saidperiphery of said base structure, and wherein said sensing meansincludes a plurality of spring loaded fingers to detect said recesses.6. A lamp assembly according to claim 4, wherein said encoding meansincludes a plurality of projections at said periphery of said basestructure, and wherein said sensing means includes a housing structureat said periphery containing oppositely disposed light emitting diodesand photodiodes for detecting said projections.
 7. A lamp assemblyaccording to claim 2, wherein said encoding means includes a structurehaving said projections and recesses, and wherein said structure isattached to said base structure.
 8. A lamp assembly according to claim7, wherein reading means is provided for reading said structure andproviding identification by said connecting means.
 9. A lamp assemblyaccording to claim 8, wherein said reading means includes a housing witha slot into which said structure is inserted, and wherein said housingincludes internal sensing means for sensing said projections andrecesses.
 10. A lamp assembly according to claim 9, wherein saidinternal sensing means includes an array of light emitting diodesarranged opposite an array of photodiodes, said structure being insertedbetween said light emitting diodes and said photodiodes.
 11. A lampassembly according to claim 1, wherein said encoding means includes anencoded magnetic strip to represent said at least one atomic element.12. A lamp assembly according to claim 11, wherein magnetic code readingmeans is provided for reading said encoded magnetic strip and providingidentification by said connecting circuit means.
 13. A lamp assemblyaccording to claim 11 or claim 12, wherein said lamp means includes abase structure, and wherein said encoded magnetic strip is provided on astructure attached to said base structure.
 14. A lamp assembly accordingto claim 1, wherein said encoding means includes an encoded optical barcode to represent said at least one atomic element.
 15. A lamp assemblyaccording to claim 14, wherein optical code reading means is providedfor reading said encoded optical bar code and providing identificationby said connecting circuit means.
 16. A lamp assembly according to claim14 or claim 15, wherein said lamp means includes a base structure, andwherein said encoded optical bar code is provided on a structureattached to said base structure.
 17. A lamp assembly according to claim1 or claim 4 or claim 11 or claim 14, wherein said lamp means producesresonance lines characteristic of a single element hollow cathode lamp.18. A lamp assembly according to claim 1 or claim 2 or claim 11 or claim14, wherein said lamp means produces resonance lines characteristic of amultiple element hollow cathode lamp.
 19. A lamp assembly according toclaim 1 or claim 2 or claim 11 or claim 14, wherein said lamp meansincludes electrodeless discharge lamps.
 20. A lamp assembly according toclaim 1 or claim 2 or claim 11 or claim 14, wherein said encoding meansalso represents lamp current.
 21. An atomic absorption spectrophotometercomprisingsource lamp assembly means for producing radiationcharacteristic of at least one atomic element, said source lamp assemblymeans including lamp means for producing resonance line radiationcharacteristic of said atomic element, encoding means for representingat least said radiation, and connecting circuit means for connectingsaid encoding means to a circuit enabling identification of said atleast one atomic element, measurement circuit means for identifying saidatomic element, said measurement circuit means being connected to saidencoding means through said connecting circuit means, atomizer means foratomizing samples to be analyzed by said radiation, monochromatorcircuit means for providing measurement wavelengths of said samples,said monochromator circuit means including a monochromator receivingradiation passed by said atomizer means, detector means for detectingsaid measurement wavelengths, said detector means being connected tosaid measurement circuit means microcomputer circuit means connected toelements of the spectrophotometer for controlling saidspectrophotometer, said microcomputer means including microprocessormeans for identifying said atomic element and for applying informationto said monochromator circuit means, and read-only memory circuit meansfor holding wavelength information associated with said atomic element,said wavelength information being applied to said monochromator circuitmeans by said microprocessor means.
 22. A spectrophotometer according toclaim 21, wherein said encoding means represents lamp operating currentfor said lamp means.
 23. A spectrophotometer according to claim 22,wherein lamp power supply means for operating said lamp means areprovided, and wherein said read-only memory circuit means holds lampcurrent information, said microprocessor means controlling said lamppower supply means by lamp current information from both saidmeasurement circuit means and said encoding means and by said lampcurrent information from said read-only memory circuit means.
 24. Aspectrophotometer according to claim 21, wherein read-write memorycircuit means is provided for continuously storing at least oneinformation set, said microprocessor means controlling said lampassembly means with said information set for analyzing said samples withrespect to said at least one atomic element, said microprocessor meansusing said information set for at least a duration of analysis, andwherein said information set has atomic element information derived fromsaid read-only memory circuit means, and from other sample relatedinformation.
 25. A spectrophotometer according to claim 24, whereinholding and positioning means are provided for holding a plurality ofsaid lamp assembly means each having said encoding means being connectedto said measurement circuit means, said holding and positioning meansbeing provided for positioning one lamp means at a time of saidplurality of lamp assembly means in an optical path of both saidatomizer means and said monochromator circuit means, and wherein saidmicroprocessor means controls said holding and positioning means toposition said radiation characteristic of each atomic element in saidoptical path, said microprocessor means using each of a plurality ofsaid information sets in turn, said plurality of information sets beingcontinuously stored in said read-write memory circuit means at least forsaid duration of analysis.
 26. A spectrophotometer according to claim 21or claim 22 or claim 23 or claim 24 or claim 25, wherein said lamp meansincludes a base structure, and wherein said encoding means include aplurality of at least one of projections and recesses to represent saidat least one atomic element.
 27. A spectrophotometer according to claim26, wherein said encoding means is located on a periphery of said basestructure.
 28. A spectrophotometer according to claim 29, whereinsensing means are arranged for detecting said projections and recesses.29. A spectrophotometer according to claim 28, wherein said encodingmeans includes a plurality of recesses at said periphery of said basestructure, and wherein said sensing means includes a plurality of springloaded fingers to detect said recesses.
 30. A spectrophotometeraccording to claim 28, wherein said encoding means includes a pluralityof projections at said periphery of said base structure, and whereinsaid sensing means includes a housing structure at said peripherycontaining oppositely disposed light emitting diodes and photodiodes fordetecting said projections.
 31. A spectrophotometer according to claim26, wherein said encoding means includes a structure having saidprojections and recesses, and wherein said structure is attached to saidbase structure.
 32. A spectrophotometer according to claim 31, whereinreading means is provided for reading said structure and providingidentification by said connecting means.
 33. A spectrophotometeraccording to claim 32, wherein said reading means includes a housingwith a slot into which said structure is inserted, and wherein saidhousing includes internal sensing means for sensing said projections andrecesses.
 34. A spectrophotometer according to claim 33, wherein saidinternal sensing means includes an array of light emitting diodesarranged opposite an array of photodiodes, said structure being insertedbetween said light emitting diodes and said photodiodes.
 35. Aspectrophotometer according to claim 21 or claim 22 or claim 23 or claim24 or claim 25, wherein said encoding means includes an encoded magneticstrip to represent said at least one atomic element.
 36. Aspectrophotometer according to claim 35, wherein magnetic code readingmeans is provided for reading said encoded magnetic strip and providingidentification by said connecting circuit means.
 37. A spectrophotometeraccording to claim 35, wherein said lamp means includes a basestructure, and wherein said encoded magnetic strip is provided on astructure attached to said base structure.
 38. A spectrophotometeraccording to claim 21 or claim 22 or claim 23 or claim 24 or claim 25,wherein said encoding means includes an encoded optical bar code torepresent said at least one atomic element.
 39. A spectrophotometeraccording to claim 38, wherein optical code reading means is providedfor reading said encoded optical bar code and providing identificationby said connecting circuit means.
 40. A spectrophotometer according toclaim 38, wherein said means includes a base structure, and wherein saidencoded optical bar code is provided on a structure attached to saidbase structure.